Grinding wheels of various shapes, sizes, and composition are well known in the art. Wheels containing superabrasive materials such as diamond or cubic boron nitride (CBN) in the grinding edge of the wheel are specialty wheels used in certain commercial processes. For example, such superabrasive wheels are used in cutting operations including dicing, slicing, scribing, slotting and squaring in the processing of silicon wafers in the electronics industry. Superabrasive cutting wheels are used to perform these cutting operations on hard alumina coatings on such wafers. To avoid thermal and mechanical stress or damage to the circuit, cutting operations are performed using superabrasive cutting wheels at a slow rate. One of the principal costs involved in the production of such circuits is the cutting operation including the time and costs of replacing worn wheels.
Accordingly, an effort has been made to improve the grinding performance of superabrasive wheels by increasing their wear resistance and grinding ability. Such efforts have been concentrated in the area of compositional changes including adding fillers, using various combinations of superabrasives and changing the bonding agents. Examples of suitable bonding agents that have been employed include phenolic resins, epoxy resins, polyester resins, shellac, polyimide and rubber. Phenolic resins are presently the most widely used polymeric bonding agents for superabrasive wheels.
Recently, CA 107(24):221,932k, 1991 reported the use of a polyaminobismaleimide resin as an improved bonding agent for diamond wheels used in the polishing of ceramics.
A cutting wheel containing Borazon.RTM. II cubic boron nitride of General Electric and N,N'-(p,p'-methylenediphenylene)bismaleimide-p,p'-methylenedi-aniline copolymer is disclosed as being useful for the dry cutting of tool steel. See CA 78(20):125,612t.
Japanese Patent Application No. 77044078 discloses a diamond wheel containing a mixture of specific polyoxybenzoyl resins and polybismaleimide resins in combination with a carbon fiber or solid lubricant such as molybdenum disulphide or graphite.
While grinding wheels offering improved efficiency have been produced, there is still room for further improvement in grinding rate and/or cutting rate and/or efficiency.
Accordingly, it is an object of the present invention to prepare a high precision superabrasive wheel having an improved grinding or cutting rate and with high grinding or cutting efficiency so as to use the same or less power, thereby reducing processing costs.
It is another object of the present invention to design a superabrasive wheel with superior wear resistance.